Various types of compressed gas including breathing oxygen are distributed in cylinders under pressures that are higher than those at which the gas is normally used. The user applies to the valved end of the cylinder a gas pressure regulator assembly to reduce pressure. The assembly includes a mounting yoke which clamps onto the cylinder valve structure and connects the compressed gas to the regulator upon opening a valve. Tubing for conducting the gas to the end user of the gas at a desired pressure is connected to the regulator outlet.
When the cylinder of gas is empty, the regulator assembly is removed, the gas cylinder is returned to the supplier of the gas for refilling, while the regulator is available for use on another filled cylinder. Because of this refilling and reusing distribution procedure, it is important that a regulator be quickly and easily mounted on a cylinder in emergency situations by a variety of personnel having greatly differing degrees of familiarity with the equipment and manipulative skill in operating it. The regulator assemblies must, therefore, be easy to operate and yet be rugged and durable for many years of use, including repeated mountings and dismountings to the gas cylinders. Because it is critical that the proper gas be utilized with a particular regulator and patient, each cylinder is provided with indexing holes in which indexing pins in the mounting yoke must fit before the yoke can be clamped in position.
The Compressed Gas Association, Inc. has established precise standards concerning the pin indexed yoke construction and the size and location of the pins, as well as other requirements. Similarly, an international organization specifies requirements for yoke and regulator construction. Examples of these are set forth in a document identified as ISO 407-1983(E). Some of these requirements are: (1) a gas tight seal shall only be possible when the pins in the yoke correspond to the holes in the valve; (2) when the pins in the yoke do not correspond to the holes in the valve, a gas tight seal shall not be possible and damage to the yoke or the valve shall be prevented; (3) pins shall not be removable or assembled in such a manner that they can become loose in service; (4) the yoke shall be able to resist, without permanent deformation, the load resulting from a specified torque applied to the valve clamping screw or locking device; and (5) the dimensions of the yoke shall limit the movement of the valve in the yoke to a maximum of 6.degree. about the vertical axis prior to pin engagement.
Typically, regulator yokes have a rectangular U-shaped or closed loop construction that fits onto a mating valve outlet on the cylinder. One end of the yoke is attached to the regulator, and the other end of the yoke typically includes a large hand-manipulatable clamping screw by which the yoke and the regulator are tightly clamped to the cylinder. The prior art yokes are made in various ways, but seem to fall into three categories. Perhaps most commonly, the yokes are forged or cast into the basic closed rectangular loop-shape and various machining operations are then performed. This includes drilling and tapping one end of the yoke in which to mount the clamping screw, drilling a hole in the base end of the yoke for connection to a regulator stem, drilling one or more indexing pin holes in the base end of the yoke, and installing the indexing pins, usually in a press fit operation. With many yokes of this type, the process is completed with a plating or other finishing step. While yokes of this type have proven to be rugged and reliable, they are relatively expensive from a standpoint of manufacturing labor and materials. Also, the tapped threads for receiving the clamping screw are ruined after a period of time because of wear and excess clamping force, with the result that the entire yoke is discarded.
Another type of yoke construction which represents a cost improvement over the cast-type is that initially made by extrusion. An example of this is illustrated in U.S. Pat. No. 4,020,863--Fabish. In that construction, a length of yoke is extruded with the desired U-shaped cross section. Individual yokes are then sliced from this extrusion, and the closed end of the U-shaped yoke is drilled and tapped for receiving the clamping screw. The open ends of the yoke are attached directly to the regulator body by suitable fasteners. Indexing pin holes are drilled in the regulator body, and pins press fit therein. While the extruded construction is relatively cost-effective from a fabrication standpoint, it is less versatile in that the regulator body is limited to use with a yoke of that type. By contrast, those yokes having the closed loop construction can be removed relatively easily from the regulator such that the regulator may be used in connection with a completely different type of connecting structure employing a nut-type tightened nipple construction, sometimes referred to as a "bull nose."
A third type of yoke construction is that which is totally machined, either separate from or integral with a regulator body. For example, in one construction, the yoke is formed by machining a large opening in cylindrical stock with the closed loop opening corresponding to the desired size for the yoke. It is then necessary to drill and tap threads in the handle end for receiving the clamping stem handle and to drill holes in the base end for receiving indexing pins, which then have to be installed as an additional step. As an alternate variation of the machine construction, the clamping screw receiving hole is not tapped, but instead, a tubular bolt or bushing is mounted in the hole and held in position by a nut. The bolt is internally threaded to receive the clamping screw. This machined construction has certain advantages over the cast or forged approach, but is not separatable from the regulator, such that the regulator cannot be used with the other mounting device referred to above.
Because of the large volume of regulator yokes being marketed and the competitive nature of the business, a need exists for an improved, less expensive construction that nevertheless meets all of the various requirements for ruggedness, durability and safety, and also has versatility that permits the regulator to be readily separated from the yoke.